Devices for storing and providing electrical power have been in use for a long time. Generally falling under the descriptor “battery,” such devices include electro-chemical cells and collections of cells that provide an electrical potential between at least a set of terminals. The terminals can be connected to an electrical (e.g. direct current, DC) load to energize or power the load. Batteries include dry cells, wet cells (e.g. lead-acid cells), and other types of units that generally convert a chemically available electromotive force into a current.
Batteries are sometimes classified into “primary” and “secondary” types. Primary batteries are single-use units that come from a manufacturer with a limited electro-chemical capacity and are exhausted and discarded after use. Secondary batteries can be “recharged” after use, and while not infinite in their capacity, allow for repeated use of the same cell through reversing the discharge process to some extent.
To increase battery capacity, cells have been configured to take advantage of a large surface area between the anode (negative) and cathode (positive) elements of the cells. One such design involves placing many parallel plates in electrolyte solution to allow for ionic transfer between the anodes and cathodes, generally referred to as “prismatic” cells.
Another design separates planar layered sheets of anode and cathode materials with porous membranes, then rolls the layers into a roll, referred to as a “jelly roll” that provides a compact and mechanically stable battery, generally referred to as “cylindrical” cells. In rolled battery designs, multiple alternating sheets of anode, separator, and cathode materials are used as permitted by the spatial considerations of the battery, and the anode sheets are collectively connected to an anode terminal while the cathode sheets are collectively connected to a cathode terminal. The entire device is packaged in a rigid enclosure, usually a cylindrical can.
In order to provide electrical connections to the battery terminals, multiple conducting tabs typically are inserted by welding at carefully selected intervals within the structure before it is rolled up. Prior art tabbed jelly rolls having thirty windings typically have about six tabs for each of the anode and cathode. Some designs have only one tab for each of the cathode and anode. Because the tabs are welded prior to rolling, the tabs must be precisely placed and the jelly roll must be precisely wound in order to create aligned tabs in the final rolled cell.